Numerous patents have disclosed coatings for sweeteners in an attempt to delay or prolong sweetness, as well as to stabilize those sweeteners, such as aspartame, which are sensitive to moisture, temperature and pH. U.S. Pat. No. 4,384,004 to Cea et al., discloses solid particles of aspartame encapsulated by a coating material selected from the group consisting of cellulose, cellulose derivatives, arabinogalactin, gum arabic, polyolefins, waxes, vinyl polymers, gelatin, zein and mixtures thereof, wherein the amount of said coating material to said methyl ester is from 1:1 to 1:10. More particularly, the coating materials include cellulose, methyl cellulose, ethyl cellulose, cellulose nitrate, cellulose acetate phthalate, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, arabinogalactan; polyethylene, polymethacrylates, polyamides, ethylenevinyl acetate copolymers, polyvinylpyrrolidone; gum arabic; paraffin wax, carnauba wax, spermaceti, beeswax; stearic acid, steryl alcohol, glyceryl stearate; gelatin, zein and mixtures thereof.
The method of coating employed in this reference includes suspending the aspartame particles in a stream of air that passes through a zone of atomized liquid droplets of the coating material, so that the coating material is deposited on the surface of the aspartame. More than one coating may be used whereby the inner coating is water-soluble and the outer coating is water-soluble.
U.S. Pat. Nos. 4,122,195 and 4,139,939, both to Bahoshy et al., fix aspartame by preparing it with a material such as gum arabic or the reaction product of a compound containing a polyvalent metallic ion, with an ungelatinized start acid-ester of a substituted dicarboxylic acid, by a spray drying technique, where the aspartame and a film former are prepared in an emulsion.
U.S. Pat. No. 4,374,858, to Glass et al., discloses an aspartame sweetened chewing gum having improved sweetness stability wherein the chewing gum piece has aspartame coated on its surface, as opposed to incorporating it in the chewing gum mix.
EPA No. 81110320.0, published June 16, 1982 (Publication No. 0053844), to Ajinomoto Co., Inc., discloses a stabilized dipeptide-based sweetening composition comprising (a) from 20 to 60% by weight of sold fat, (b) from 10 to 30% by weight emulsifier, (c) from 10 to 30% by weight polysaccharide and (d) not more than 30% by weight of dipeptide sweetener. The compositions are prepared by heating the mixture of the ingredients, cooling, and pulverizing to obtain powder or granules of the composition to obtain a ASTM mesh size of smaller than 12. Spray drying the mixture is also disclosed.
U.S. Pat. No. 4,105,801 to Degliotti, discloses a confectionery comprising a core portion and a shell adheringly enveloping the core portion, whereby the shell is formed by an intimate mixture of microcrystals of xylitol with a solid fatty substance in a proportion of 0.5 to 15 parts by weight of fatty substance to each 100 parts by weight of xylitol. The fatty substance is preferably a mono-, di- or triglyceride having a melting range of between 20.degree. and 60.degree. C.
U.S. Pat. No. 3,389,000 to Toyonaka et al., discloses protective coatings for granular nucleoside-5-phosphates, the coatings being edible fats melting between 40.degree.-100.degree. C. and derived from plants and animals. Hydrogenated oils such as soybean oil, cottonseed oil, almond oil, castor oil, linseed oil, mustard oil, olive oil, grapefruit seed oil, palm oil, palm kernel oil, rapeseed oil, rice bran oil and the like and mixtures thereof. This reference discloses a process of preparing the granular product from a liquid mixture of fats and nucleoside-5-phosphates which are sprayed from a pressure nozzle and the resultant granules cooked and recovered.
U.S. Pat. No. 4,382,924, to Berling, discloses liquid oral dosage forms for vitamins or pharmaceutical materials comprising an edible oil, a high potency lipid soluble sweetener such as saccharin and a lipid soluble flavorant. The edible oil may be a polyol fatty acid ester having at least four fatty acid ester groups and each fatty acid having from about 8 to about 22 carbon atoms. The oil, sweetener and flavor oil are mixed and heated and then cooled to provide a palatable liquid dosage form.
For a general discussion of spraying fatty materials onto sweeteners and the like see U.S. Pat. Nos. 3,949,094 and 3,976,794 both to Johnson, and 3,867,556 to Darragh. U.S. Pat. No. 4,293,572 to Silva et al., discloses the application of a dispersion of an emulsified fat with a solution of dextrin. saccharin or a polysaccharide to a food product as a barrier against moisture. U.S. Pat. No. 3,527,647 discloses a process of agglomerating particles by randomly scattering and spraying moistened particles to cause them to collide and form agglomerates.
The problem relating to stabilization of sweeteners such as aspartame, which has not been previously addressed, relates to the wettability of the aspartame crystal as well as to its morphological configuration. Aspartame is known to be rod-like, needle-like or dendritic in shape. As a result it is very difficult to coat aspartame using ordinary mixing or spray coating techniques. To be effective as protective barriers, coatings must be able to wet and adhere to the crystalline surface, including the needle-like tips and other shape variations of the aspartame. Additionally, the coating must be capable of being applied in a film with a uniform thickness sufficient to provide a barrier against degradative factors such as moisture, pH changes, temperature changes and reactive chemicals. The coatings, in addition to being protective barriers, must be flexible enough to conform to the surface irregularities and geometrical configuration without cracking due to mechanical stresses which it is subjected to during incorporation of the sweetener into specific product applications. Attempts to coat aspartame using spray techniques to apply simple mixtures of fat and lecithin have resulted in poor wetting, spotty coating and inadequate protection against moisture and other potentially degradative factors.
It has been discovered that simple mixing of known coating materials such as fats, with certain other core materials such as aspartame does not provide adequate protection to keep the core material in a stabilized state. Fats do not provide adequate coating materials, nor do such coating materials as starch, and certain other materials such as waxes. Many of these materials require solvents and moisture for application, which have adverse effects on the stability of hyrophilic instable materials such as aspartame. For example, simple mixing of aspartame in liquid mixtures of traditional coating materials, e.g., fat and lecithin, has resulted in poor wetting, spotty coating and inadequate protection against moisture and chemicals. The result was degradation of the aspartame upon exposure to these conditions. Changes in pH and temperature catalyze these degradative conditions.
The process of EPA No. 81110320.9 (Publication No. 0053844) filed Dec. 10, 1981, discussed above, is an example of simple admixing of coating materials with aspartame. This publication discloses the simple melting and admixing of from 20 to 60% of solid fat 10 to 30% of emulsifier, 10 to 30% of polysaccharide and not more than 30% dipeptide sweetener. The mixture is then cooled and pulverized or spray dried. The pulverizing into fine powder, however, results in rupturing of the coating, leaving the aspartame exposed. Spray drying is normally associated with the driving off of moisture or solvents.
U.S. Pat. No. 4,597,970 discloses a delivery system wherein a sweetener is coated with a mixture of fatty acid or wax, leithin and monoglyceride. The delivery system of this reference discloses a method of protecting the sweetener as well as providing controlled release.
The instant invention seeks to provide coating compositions which eliminate the need for fatty acid or wax components, yet still provides adequate protection and delayed release of the sweetener or other active contained therein.
The prior art techniques for coating difficult-to-coat materials such as aspartame, has focused on two methods. The first method involves the formation of a molten mixture of the coating material with the sweetener. The mixture is then solidified by cooling and pulverized. The resultant particles represent a random attempt at completely coating or enrobing the sweetener. In the case of aspartame, this coating does not provide adequate protection against moisture or aldehyde-containing flavor oils and instability of the aspartame results.
The second conventional prior art technique for coating materials involves fluidized bed spray coating. This technique involves suspending a mass of the material to be coated into a stream of atomized droplets of coating material. In the case of materials such as aspartame, this method is very difficult. Aspartame is a low density material, has a large surface to weight ratio and poor wetting characteristics. For these reasons, spray coating of aspartame in a fluidized bed system is difficult.
The instant process is an improvement over spray congealing techniques. The resultant product exhibits a marked improvement in the effectiveness of the coating as a protective barrier. The result is a significant improvement in the stability of the core (sweetener) material.
Thus, the delivery systems of the invention and process of preparation provide an improved protective coating for core materials, thereby increasing the stability of the final product. The delivery systems have a variety of other advantages including the controlled release of materials such as sweeteners and flavoring agents. Other advantages will become apparent herein.